Tools

• MapShaper is software for editing Shapefile, GeoJSON, TopoJSON and several other data formats, written in JavaScript.
• geojson.io is a quick, simple tool for creating, viewing, and sharing maps. geojson.io is named after GeoJSON, an open source data format, and it supports GeoJSON in all ways - but also accepts KML, GPX, CSV, GTFS, TopoJSON, and other formats.
• GeoJSONLint is an app that validates your GeoJSON and shows your feature(s) on a map if everything checks out ok.
• RawGit - serves raw files directly from GitHub with proper Content-Type headers.
• QGIS - A Free and Open Source Geographic Information System.